Schematic view of calcium channels and transporters in the rod-photoreceptor. Abbreviations: CNGC, cyclic-nucleotide-gated cation channel; VGCC: voltage-gated calcium channel; PMCA: plasma membrane calcium ATPase; SOCE: store-operated calcium entry; ER: endoplasmic reticulum; SERCA: sarcoplasmic-endoplasmic reticulum Ca²⁺-ATPase; IP3R: inositol 1, 4, 5-triphoaphate receptor; RyR: ryanodine receptor. Ca²⁺  stock and release from the mitochondria are mediated by Ca²⁺  uniporter channels and Na⁺/Ca²⁺  transporters.